When a sound closer to a natural musical instrument is to be generated in an electronic musical instrument, it is necessary to collect and faithfully reproduce an original sound. For example, in an acoustic piano and so on such as a grand piano, it is known that a keyboard is played and a hammer hits a string, and then, a string in harmonic relation with the hit string and a soundboard resonate to thereby generate a resonance. An actual acoustic piano generates a rich musical sound by generating various resonances as stated above in addition to the original sound.
Consequently, for example, a technique stated below is proposed in Patent Document 1, to obtain such resonance effect in the electronic musical instrument.
Namely, in the above-stated Patent Document 1, a technique in which a resonance generated by a keystroke sound is additionally sound generated when a key in a specific relation with a depressed key is stroked, to thereby generate a performance sound close to the performance sound of the acoustic piano, is proposed.
In the electronic musical instrument described in the above-stated Patent Document 1, an idea in which a resonance is sound generated in addition to a keystroke sound is disclosed, but a way how to sound generate the above-stated resonance to be added is not thought out. Consequently, there was a problem that it is difficult to obtain a sharp contour and clear sound quality because there is no scheme when the above-stated original sound and the resonance are outputted, and therefore, the sounds are mixed together, even though the resonance is added to generate the performance sound close to the acoustic piano.
Consequently, in case of the electronic musical instrument described in the above-stated Patent Document 1, there was a limit to reproduce a spread and rich musical sound in which the resonance peculiar to the natural musical instrument such as the acoustic piano is added.    Patent Document 1: Japanese Patent Application Laid-open No. Hei 6-118956